A Distributed Antenna System (DAS) is a network of spatially separated antenna nodes connected to a common node via a transport medium that provides wireless service within a geographic area or structure. Common wireless communication system configurations employ a host unit as the common node, which is located at a centralized location (for example, at a facility that is controlled by a wireless service provider). The antenna nodes and related broadcasting and receiving equipment, located at a location that is remote from the host unit (for example, at a facility or site that is not controlled by the wireless service provider), are also referred to as “remote units.” Radio frequency (RF) signals are communicated between the host unit and one or more remote units. In such a DAS, the host unit is typically communicatively coupled to one or more base stations (for example, via wired connection or via wireless connection) which allow bidirectional communications between wireless subscriber units within the DAS service area and communication networks such as, but not limited to, cellular phone networks, the public switch telephone network (PSTN) and the Internet. A DAS can provide, by its nature, an infrastructure within a community that can scatter remote units across a geographic area for providing wireless services across that area.
A digital DAS is a system wherein the host unit and remote units transport radio signal information to one another by digital means (for example, by digitally sampling a wireless radio frequency (RF) spectrum at a remote unit and transmitting the digital sample data to the host unit by fiber optics). One problem with the digital DAS occurs when radio signals of interest within the RF spectrum are separated by bandwidths containing no signals interest. In that case, fiber bandwidth within the digital DAS is wasted because all of the digital samples need to be transported at a rate sufficient to cover the full range of frequencies, not just the portions containing signals of interest.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for improved systems and methods for digital RF transport.